REL3D / NT98 S-band magnetron (E1189) (see the end of this page for an internal view)

The magnetron measures 190x75mm overall, plus leads, and weighs 550g.

E1189 was developed in mid-1940 from E1188, which was itself developed from Randall and Boot's original cavity magnetron. It was the first magnetron suitable for use as a radar transmitter. The first E1189 was 6-segment but was redesigned as 8-segment, and an example was taken to the USA by the Tizard Mission in August 1940.

Used in Naval Radar Type 271, the E1189 was later standardised as NT98. The REL3D is equivalent.

See also REL3C (E1198/CV38)

Both faces of the magnetron, showing the serial number 7665, and the marking J24 R.E.L.

Internal views

REL3D serial 7427 opened up. The output port is on the right but this magnetron was damaged and the output loop has been distorted. Below is the cathode and heater. The cathode cylinder measures approx. 22x5mm, the heater coil was supported at each end by the fittings shown, and a mica insulator was placed between the end of the heater and the metal plate that forms the side of the magnetron. Shown also is one of the glass lead seals.